Zirconium alloy



Feb. 7, 1928. x 1,658,712

G. R. FONDA ZIRGONIUM ALLOY Filed Aug- 30. 1924 InVentOr-z GQrtOY R. f-CNW da, by IHs Attorney.

Patented Feb. 7, 1,928.

UNITED STATES PATENT OFFICE.

GORTON R. FONDA, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION F NEW YORK.

ZIRCONIUM ALLOY.

Application rled August 30, 1924. Serial No. 735,075.

rIhis application is a continuation in part of my prior applicationfiled July 29, 1920, Serial No. 399,798.

-The present invention relates to the formation of alloys of zirconiumand in particular to the formation of zirconium alloy of a highlyvrefractory metal, such as tungsten. My invention is particularlyapplicable to the manufacture of Wire-shaped or filamentlo ary bodies ofzirconium alloy' and in particular to the manufacture of lightingfilaments comprising a preponderant amount of tungsten and a lesserproportion of zircomuni.

It has been suggested heretofore to prepare alloys of tungsten andzirconium by mixing these metals in finely powdered form, consolidatingthe same by heating and finally forming wires by swaging and zo drawing.My experience has indicated that an alloy of tungsten and zirconiumcannot be easily worked into the form of filament-ary bodies by suchmechanical process.

In accordance with my invention these alloys are prepared moreconveniently by rst coating a foundation metal, such as tungsten, with alayer of zirconium in a dense, finely crystalline, adherent form, andthereupon at a higher temperature causing diffusion of the zirconiuminto the foundation metal. Under these conditions I find that asubstantial homogeneous alloy is formed of the foundation metal and thezirconium coating.

'lhe accompanying drawing shows in elevation and in simplified form, anapparatus for carrying out the coating process.

My invention Will be illustrated by describing the manufacture oflighting bodies suitable for use in incandescent lamps, and consistingof a preponderant amount of tungsten and a lesser amount of zirconium.In the production of such lighting bodies, wires or filaments oftungsten are first prepared, for example, by the procedure described inCoolidge Patent No. 1,082,933 of December' 30, 1913. A tungsten filamentof suitable.

thickness, say of about one to four mils in diameter, on which zirconiumis tobe deposited, is heated in an enclosed space in contact with amixture of a halogen compound of zirconium, such as the chloride and agaseous reducing agent, for example, hydrogen. The

reduction may be carried out in an enclosed space, such as a treatingbottle, of the type well known in lamp filament manufacture. As shown inthe drawing, a filament f1 is mounted upon. spring clip terminals 2, 2supported from a .stopper 8 within a container 4; having gas inlet andoutlet tubes 5, (5. A simple hair-pin shaped filament has been shown forpurpose of illustration but of course, the filament may have any desiredshape. rlhe reduction zone is maintained at atemperature of about 300oC. or somewhat higher, for example, by a suitable external heater asindicated by the dotted outline 8. The hydrogen is passed through thebottle at the speed best adapted to give a finely crys talline depositon the filament. For ex- 70 ample, in a bottle about 11/1 inch indiameter, a stream of hydrogen is conducted over the zirconium compound7 and in contact with the tungsten filament at a rate of about 150 to200 cc. per minute. At a lower rate of hydrogen flow the deposit becomesfeathery or fuzzy, at a higher rate of flow the alloy becomes coarselycrystalline and poorly adherent. Neither condition is well adapted forthe subsequent alloying step. The tungsten filament should be heated toa temperature between bright redness and a. ywhite incandescence (about1500o C.) for example by passage of current supplied by the conductors9, 10. Here likewise a lower temperature tends to produce a feathery deposit. A higher temperature produces a coarsely crystalline deposit.After the required amount of zirconium has been deposited, reduction isinterrupted, and the coated filament is removed.

V I prefer to deposit suilicient zirconium upon the lfilament to producean alloy which may vary Within the limits of 0.5 to 4 per cent ofzirconium content, although the pref- 95 erable percentage is in theneighborhood of about 3 per cent. The amount of zirconium may beaccurately predetermined by trial and will depend upon the conditions ofthe reduction, such as the rate of flow of the 100 hydrogen, thetemperature and therefore the vapor pressure of the zirconium compoundand the temperature of the filament. In ease of the above mentionedconditions 3 per ceit of zirconium is deposited in a few sec- 105 on s.

The zirconium coated filament, after bein removed from contact with thereduction mixture, is heated referably in contact with a gas, suoli ashy rogen or argon which is inert with respect to the coated filament, orin vacuum, to a tem erature at which a homogeneous alloy is ormed whilethe filament remains intact. In the case of the described tungstenfilament coated with about 3 per cent of zirconium, the filamentpreferably should be heated to about 26000 C. for a few minutes to bringthis about. This is a temperatuie well above the ordinary operatingtemperature of an incandescent lamp when emitting light at an efficiencyof about one watt per candle which is about 21.50 C'. When a temperatureless than 2600o C. is einployed the length of time of heating should belengthened accordingly. If desired the unalloyed composite filament oftungsten and zirconium may be mounted directly in an incandescent lampin the usual well understood manner and the alloyage then will occurduring the normal operation of the lamp. If the lamp is operated at anefiiciency of about one watt per candle the alloyage will requireseveral hours to become complete. Of course, as the lamp in the meantimeis being used in a normal manner, this slow alloyage is notobjectionable.

The presence of the zirconium in the filament lowers the rate ofevaporation during operation at incandescence as compared with anunalloyed tungsten filament.

When operating in a lamp at bright incandescence, at a given efficiencythe alloyed 'zirconium lengtliens the life of the filament or if thesaine average life is desired as obtainable with the unalloyed tungstenfilament, the zirconium alloy filament may be operated at a higherefficiency.

When a zirconium alloy filament is used in a gas-lled lamp, such asdescribed in Langmuir Patent No. 1,180,159, issued April 18, 1916, thefilament. burns to a greater decrease in weight before burning out thanan unalloyed tungsten filament.

Metallic zirconium may be deposited on the foundation by methods otherthan chemical deposition. The zirconium layer may be mechanicallydeposited. For example, a filament of tungsten, or other metal alloyablewith zirconium may be coated with a suspension of finely dividedzirconium in a suitable medium such as a solution of film stock whichconsists mainly of cellulose Jacetate or other cellulose compound. The

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

l. The process of preparing an alloy of tungsten and zirconium whichconsists in forming on tungsten alayer of zirconium by the thermaldecomposition of a zirconium compound, interrupting the reaction andthereupon heating the tungsten and zirconium to a higher temperature atwhich alloyage occurs iii an environment inert with respect to saidmetals.

2. The process of preparing filamentary bodies comprising an alloy oftungsten and zirconium which consists in heating the filament of'tungsten in the presence of the va or of a zirconium compound and areducing agent at a temperature at which the metallic zirconium isdeposited on said filament, removing the coated filament from contactwith the zirconium compound, and then heating to a temperature at whichalloyage oc curs between the tungsten filament and zir conium coating.

3. The process of preparin an alloy of tungsten and zirconium whicconsists in depositing metallic zirconium on a foundation of tungsten ata temperature of about 15500o C. and then heating to a material] highertemperature in an environment wliic i is inert with respect to saidmetals.

4. The process of preparing a filamentary body consisting of an alloy oftungsten and zirconium which consists in depositing on a tungstenfilament a layer of zirconium by heating said filament to about 1500" C.in Contact with a gaseous mixture of a zirconium compound and a reducingagent, and thereupon heating the coated filament to a temperature of atleast about 2600 C. to cause diffusion and alloyage of the zirco nium.

5. The process of preparing an alloy of zirconium with a highlyrefractory metal which consists in depositing a layer of zir conium onsaid metal by reduction of a vaporized zirconium compound at a temperature at which the zirconium is deposited as a dense, adherent, unalloyedlayer and then heating to a higher temperature at which an alloy ofsubstantially uniform composi tion is formed.

6. The process of preparing an alloy of tungsten and zirconium whichconsists in heating a tun sten filament in contact with a current ofzirconium halide and hydrogen gas, maintaining the temperature of saidfilament, and the rate of flow of said gas at such values that a dense,adherent, finely crystalline coating of zirconium is formed and heatingsaid coated filament to a temperaturesufiiciently high to causealloyage.

7. The process of preparing a filamentary body consisting of an alloy oftungsten and zirconium which consists in heating a tungsten filament ina mixture of zirconium chloride and hydrogen, maintaining said gaseousmixture in motion at such rate and maintaining the temperature of saidilament at such value that a finely crystalline coating of zirconium isformed, interrupting the deposition when a desired quantity of zirconiumhas been deposited and heating the coated filament out of contact withsaid gaseousmixture at a temperature sufficiently 10 high to causediffusion and alloyage of the zirconium in the tungsten.

In witness whereof, I have hereunto set my hand this 28th day of August,1924.

GORTON R. FUNDA.

